Add support for YOLOv4x-mish

* backport to 3.4 for supporting yolov4x-mish

* add YOLOv4x-mish test

* address review comments
Co-authored-by: NGuo Xu <guoxu@1school.com.cn>

* Supported ReduceSum op

* Skip test

add relu option

add relu as activation option in darknet

simplify the setParams if-else ladder

add relu as activation option in darknet

correct activation_param type

format

format

add relu as activation option in darknet

spacing

spacing

add relu as activation option in darknet

* Supported yolov4-tiny

* Added comments

* Support Yolov4

* Skip Mish on OpenVINO 2020.2

* Revert Mish

* Refactoring

* Support nGraph Region

* Support region since OpenVINO 2020.2

* Skip myriad

dnn(darknet-importer): add grouped convolutions, sigmoid, swish, scale_channels

* update darknet importer to support enetb0-yolo

* remove dropout (pr16438) and fix formatting

* add test for scale_channels

* disable batch testing for scale channels

* do not set LayerParams::name

* merge all activations into setActivation

Add lightweight IE hardware targets checks

nGraph: Concat with paddings

Enable more nGraph tests

Restore FP32->FP16 for GPU plugin of IE

try to fix buildbot

Use lightweight IE targets check only starts from R4

dnn(eltwise): fix handling of different number of channels

* dnn(test): reproducer for Eltwise layer issue from PR16063

* dnn(eltwise): rework support for inputs with different channels

* dnn(eltwise): get rid of finalize(), variableChannels

* dnn(eltwise): update input sorting by number of channels

- do not swap inputs if number of channels are same after truncation

* dnn(test): skip "shortcut" with batch size 2 on MYRIAD targets

* Support nGraph

* Fix resize

* Wrap unsupported by IE layers as custom layers

* Replace pointers to layers blobs to their shapes

* Enable Faster R-CNN with IE backend on CPU

misused 'optional' mode

* Remove Inference Engine 2018R3 and 2018R4

* Fix 2018R5

* Fix precision in tests for MyriadX

* Fix ONNX tests

* Add output range in ONNX tests

* Skip tests on Myriad OpenVINO 2018R5

* Add detect MyriadX

* Add detect MyriadX on OpenVINO R5

* Skip tests on Myriad next version of OpenVINO

* dnn(ie): VPU type from environment variable

* dnn(test): validate VPU type

* dnn(test): update DLIE test skip conditions